#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavdevice/avdevice.h>
#include <libswresample/swresample.h>

#define MAX_AUDIO_FRAME_SIZE 192000

int main()
{
    //注册所有的工具
    av_register_all();

    AVFormatContext *fmt_ctx = NULL;
    AVCodecContext *cod_ctx = NULL;
    AVCodec *cod = NULL;
    printf("step 2 ...........................\n");
    //分配一个avformat
    fmt_ctx = avformat_alloc_context();
    if (fmt_ctx == NULL)
        printf("alloc fail");

    printf("step 3 ...........................\n");

    cod = avcodec_find_decoder(AV_CODEC_ID_AAC);
    cod_ctx = avcodec_alloc_context3(cod);

    if (avcodec_open2(cod_ctx, cod, NULL) < 0)
        printf("can't open codec");

    //创建packet,用于存储解码前的数据
    AVPacket *packet = (AVPacket *)av_malloc(sizeof(AVPacket));

    //设置转码后输出相关参数
    //采样的布局方式
    uint64_t out_channel_layout = AV_CH_LAYOUT_MONO;
    //采样个数
    int out_nb_samples = 1024;
    //采样格式
    enum AVSampleFormat sample_fmt = AV_SAMPLE_FMT_S16;
    //采样率
    int out_sample_rate = 44100;
    //通道数
    int out_channels = av_get_channel_layout_nb_channels(out_channel_layout);
    printf("%d\n", out_channels);
    //创建buffer
    int buffer_size = av_samples_get_buffer_size(NULL, out_channels, out_nb_samples, sample_fmt, 1);

    //注意要用av_malloc
    uint8_t *buffer = (uint8_t *)av_malloc(MAX_AUDIO_FRAME_SIZE * 2);

    //创建Frame，用于存储解码后的数据
    AVFrame *frame = av_frame_alloc();

    int got_picture;

    int64_t in_channel_layout = av_get_default_channel_layout(cod_ctx->channels);
    //打开转码器
    struct SwrContext *convert_ctx = swr_alloc();
    //设置转码参数
    convert_ctx = swr_alloc_set_opts(convert_ctx, out_channel_layout, sample_fmt, out_sample_rate,
                                     in_channel_layout, cod_ctx->sample_fmt, cod_ctx->sample_rate, 0, NULL);
    //初始化转码器
    swr_init(convert_ctx);

    //每次读取一帧，并转码,这里接受webscoket的数据
    av_init_packet(packet);


    //初始化工作完成，开启socket，准备解析数据
    uint8_t *data = NULL;
    av_packet_from_data(packet, data, sizeof(data));
    //解码声音
    if (avcodec_decode_audio4(cod_ctx, frame, &got_picture, packet) < 0)
    {
        printf("decode error");
        return -1;
    }

    if (got_picture > 0)
    {
        //转码
        swr_convert(convert_ctx, &buffer, MAX_AUDIO_FRAME_SIZE, (const uint8_t **)frame->data, frame->nb_samples);

        printf("pts:%10lld\t packet size:%d\n", packet->pts, packet->size);
    }
    got_picture = 0;
    av_free_packet(packet);

    swr_free(&convert_ctx);

    return 0;
}